With the development of computer networks and the Internet, digital time stamp has been more and more important in the digital world, especially, for the electronic business activities. Digital time stamp has become an important evidence in transactions and security monitoring.
The method for generating a digital time stamp, in the prior art, comprises: first extracting a digest from the data (or file) that needs a time stamp and then attaching current time information (date and time) to the digest and making a digital signature (encryption).
Further, since the terminal computing device or the equipment of a transaction party, i.e. the local device, is usually not trusted due to technical or commercial reasons, the method for generating a trusted digital time stamp in the prior art comprises: as shown in FIG. 1, locally extracting a digest from the data (or file) that need a time stamp; next, sending the digest to a trusted digital time stamp server (DTS); then, the digest is attached with time information about the time of receiving the digest and a digital signature by the DTS and returned back as a trusted digital time stamp.
Thus, each time when generating a digital time stamp, it is necessary to communicate with a digital time stamp server. In this respect, it has been proposed to use a reliably synchronized local clock for generating a time stamp. For example, United States Patent No. US2002/0056042 disclosed such a method and system. But, the system's complexity is increased for the reliable synchronization of a local clock. United States Patent No. US2002/0056042 is incorporated herein in entirety for all purposes.